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Which is used for internal circuits of the video decoder, XTALN or XTALP?

Question asked by Tamu2 on Feb 6, 2018
Latest reply on Feb 9, 2018 by Poornima

Hello,

 

I have a question of video decoder devices.

Video decoder devices (ADV7182A, ADV7182, ADV728xA, ADV728x, ADV7180 etc.) have XTALN pin and XTALP pin.
XTALN pin is input from the external crystal.
XTALP pin outputs it to the crystal. (I think this is inverted and amplified internally from input XTALN clock.)

 

Question:
 Which is fed into the internal PLL and used for internal circuits of the video decoder?

 

I think the input(from XTALN) is fed into the internal PLL.
(I don't think the amplified XTALN clock (= XTALP) is fed into the internal PLL.)
Is this correct?
Please refer attached file "XTAL_PN_waveform.xlsx" for the reason.

 

Background:
My customer had used ADV728x-M for their automotive project.
This project has already been mass-production since one year ago.
At this time, a problem occurs at the project. It doesn't output the video data.
He found the XTALN clock does not seem to have enough amplitude, which is similar to the "Not OK XTALN waveform" in the attached file.
So they consider the peripheral circuit of the XTAL on their board but he has to explain it and convince the OEM.
Therefore, he needs your comment.

 

Thank you!
Best regards.
Tamu

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